// GenericsNote: Converted -- Using a Transformer instead of a Factory is no longer allowed.
/*
 *  Copyright 2003-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
/*
 * Class has been modified to run in the browser with GWT.
 * (IO-Methods were deleted=
 */
package org.apache.commons.collections15.map;

import java.util.Map;

import org.apache.commons.collections15.AbstractMapDecorator;
import org.apache.commons.collections15.Factory;
import org.apache.commons.collections15.FactoryTransformer;
import org.apache.commons.collections15.Transformer;

/**
 * Decorates another <code>Map</code> to create objects in the map on demand.
 * <p/>
 * When the {@link #get(Object)} method is called with a key that does not exist
 * in the map, the factory is used to create the object. The created object will
 * be added to the map using the requested key.
 * <p/>
 * For instance:
 * 
 * <pre>
 * Factory factory = new Factory() {
 *     public Object create() {
 *         return new Date();
 *     }
 * }
 * Map lazy = Lazy.map(new HashMap(), factory);
 * Object obj = lazy.get("NOW");
 * </pre>
 * <p/>
 * After the above code is executed, <code>obj</code> will contain a new
 * <code>Date</code> instance. Furthermore, that <code>Date</code> instance is
 * mapped to the "NOW" key in the map.
 * <p/>
 * This class is Serializable from Commons Collections 3.1.
 *
 * @author Stephen Colebourne
 * @author Matt Hall, John Watkinson, Paul Jack
 * @version $Revision: 1.1 $ $Date: 2005/10/11 17:05:32 $
 * @since Commons Collections 3.0
 */
public class LazyMap<K, V> extends AbstractMapDecorator<K, V>
		implements Map<K, V> {

	

	/**
	 * The factory to use to construct elements
	 */
	// protected final Factory<V> factory;

	/**
	 * The factory to use to construct elements
	 */
	protected final Transformer<K, V> transformer;

	/**
	 * Factory method to create a lazily instantiated map.
	 *
	 * @param map
	 *            the map to decorate, must not be null
	 * @param factory
	 *            the factory to use, must not be null
	 * @throws IllegalArgumentException
	 *             if map or factory is null
	 */
	public static <K, V> Map<K, V> decorate(Map<K, V> map, Factory<V> factory) {
		return new LazyMap<K, V>(map, factory);
	}

	/**
	 * Factory method to create a lazily instantiated map.
	 *
	 * @param map
	 *            Map to decorate, must not be null
	 * @param transformer
	 *            Transformer to use, must not be null
	 * @throws IllegalArgumentException
	 *             if map or transformer is null
	 */
	public static <K, V> Map<K, V> decorate(Map<K, V> map,
			Transformer<K, V> transformer) {
		return new LazyMap<K, V>(map, transformer);
	}

	// -----------------------------------------------------------------------
	/**
	 * Constructor that wraps (not copies).
	 *
	 * @param map
	 *            the map to decorate, must not be null
	 * @param factory
	 *            the factory to use, must not be null
	 * @throws IllegalArgumentException
	 *             if map or factory is null
	 */
	protected LazyMap(Map<K, V> map, Factory<V> factory) {
		super(map);
		if (factory == null) {
			throw new IllegalArgumentException("Factory must not be null");
		}
		this.transformer = new FactoryTransformer<K, V>(factory);
	}

	/**
	 * Constructor that wraps (not copies).
	 *
	 * @param map
	 *            Map to decorate, must not be null
	 * @param transformer
	 *            Transformer to use, must not be null
	 * @throws IllegalArgumentException
	 *             if map or factory is null
	 */
	protected LazyMap(Map<K, V> map, Transformer<K, V> transformer) {
		super(map);
		if (transformer == null) {
			throw new IllegalArgumentException("Transformer must not be null");
		}
		this.transformer = transformer;
	}

	@Override
	@SuppressWarnings("unchecked")
	public V get(Object key) {
		// create value for key if key is not currently in the map
		if (map.containsKey(key) == false) {
			V value = this.transformer.transform((K) key);
			map.put((K) key, value);
			return value;
		}
		return map.get(key);
	}

	// no need to wrap keySet, entrySet or values as they are views of
	// existing map entries - you can't do a map-style get on them.
}
